Internal Lamellar and Inverse Hexagonal Liquid Crystalline Phases During the Digestion of Krill and Astaxanthin Oil-in-Water Emulsions

Abstract

Krill oil represents an important alternative natural source of omega-3 (ω-3) polyunsaturated fatty acids (PUFAs). Considering the beneficial health effects of these essential fatty acids, particularly in various disorders including cancer, cardiovascular, and inflammation diseases, it is of paramount importance to gain insight into the digestibility of krill oil. In this work, we study the fate of krill oil-in-water emulsion, stabilized by sodium caseinate, during lipolysis by coupling time-resolved synchrotron small-angle X-ray scattering (SAXS) to flow-through lipolysis model. For gaining further insight into the effect of ω-3 PUFA-containing oil type on the dynamic structural features occurring during lipolysis, two additional astaxanthin oil-in-water emulsions, stabilized using either sodium caseinate or citrem, were subjected to lipolysis under identical experimental conditions. In addition to the difference in lipid composition in both oils, ω-3 PUFAs in astaxanthin oil, similar to fish oil, exist in the form of triacylglycerols; whereas most of those in krill oil are bound to phospholipids. SAXS showed the formation of highly ordered nanostructures on exposure of these food emulsions to the lipolysis medium: the detection of a biphasic feature of coexisting inverse hexagonal (H2) and lamellar (Lα) liquid crystalline phases in the digested krill oil droplets' interiors, as compared to a neat Lα phase in the digested astaxanthin oil droplets. We discuss the dynamic phase behavior and describe the suggested important role of these phases in facilitating the delivery of nutrients throughout the body. In addition, the potential implication in the development of food and drug nanocarriers is briefly described.

Formation of Self-Assembled Mesophases During Lipid Digestion

“…The absence of the L α phase during the digestion of mayonnaise in comparison to bovine milk may be due to the lower proportion of palmitic acid in mayonnaise (∼20% palmitic acid in mayonnaise, ∼37% in bovine milk) which may otherwise contribute to lamellar diffraction peaks from calcium soaps formed during digestion (Ono et al, 1970;Pham et al, 2020). In addition to mayonnaise, krill oil was also found to form structured mesophases during in vitro digestion (Yaghmur et al, 2019). Krill oil is a supplement rich in omega-3 polyunsaturated fatty acids, mainly located in phospholipids (Bottino, 1975;Clarke, 1980).…”

“…The digestion of krill oil resulted in the formation of L α to H 2 phase when studied using in vitro lipolysis coupled to SAXS (Yaghmur et al, 2019). The persistent H 2 phase at the end of the digestion of krill oil may be linked to the abundance of long-chain lipid species in comparison to other systems like that of bovine milk.…”

The influence of lipid digestion on the fate of orally administered drug delivery vehicles

“…The major studies focussing on studying selfassembly during lipid digestion using time-resolved X-ray scattering approaches are highlighted in Table 1. Earlier promising studies using steady-state measurements on laboratory-based instruments [35][36][37][38] inspired the development of synchrotron-based lipolysis models that enable high resolution diffraction studies during lipolysis of a diverse range of dilute lipid-based systems including pharmaceutical lipid formulations such as medium chain triglyceride (MCT) [39,40], milk [41][42][43], infant formula [44], mayonnaise [45] and fish oil supplements [46]. These studies are typically conducted by coupling a pH-stat model of lipid digestion to the synchrotron X-ray scattering measurement (Figure 3).…”

Preparation and Characterization of Microemulsions Based on Antarctic Krill Oil

“…Krill oil is extracted from a species of Antarctic krill, Euphausia superba , which is mainly active in the deep ocean and can be a food source for several larger marine animals (e.g., seals and whales) [ 1 ]. Krill oil (KO) is rich in omega-3 polyunsaturated fatty acid (PUFA) and has security as an unconventional food source for ω-3 PUFAs [ 2 , 3 ], generally recognized as safe (GRAS) by the American Food and Drug Administration (FDA) [ 4 ]. As the main component of the cell membrane is primarily phospholipids (PL), as compared to fish oil (FO), the long-chain ω-3 PUFAs in krill oil, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are more easily absorbed and utilized by the human body due to the combination with PL, while DHA and EPA in FO mainly exist with the combination of triacylglycerol (TAG) [ 2 , 5 , 6 ].…”

“…It is worth noting that due to the beneficial health effects of ω-3 PUFAs, KO is competitive as functional food ingredients and drug nanocarriers. Transport and delivery of various nutrients and bioactive food additives throughout the body might be facilitated, attributed to these structures [ 4 ].…”